address comments

Author: cloud-fan

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/CheckAnalysis.scala

@@ -62,10 +62,10 @@ trait CheckAnalysis {
             val from = operator.inputSet.map(_.name).mkString(", ")
             a.failAnalysis(s"cannot resolve '${a.prettyString}' given input columns $from")
 
-          case e: Expression if !e.validInputTypes =>
+          case e: Expression if e.checkInputDataTypes.isDefined =>
             e.failAnalysis(
-              s"cannot resolve '${t.prettyString}' due to data type mismatch: " +
-              e.typeMismatchErrorMessage.get)
+              s"cannot resolve '${e.prettyString}' due to data type mismatch: " +
+              e.checkInputDataTypes.get)
 
           case c: Cast if !c.resolved =>
             failAnalysis(

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Expression.scala

@@ -87,9 +87,10 @@ abstract class Expression extends TreeNode[Expression] {
     }
   }
 
-  def typeMismatchErrorMessage: Option[String] = None
-
-  def validInputTypes: Boolean = typeMismatchErrorMessage.isEmpty
+  /**
+   * todo
+   */
+  def checkInputDataTypes: Option[String] = None
 }
 
 abstract class BinaryExpression extends Expression with trees.BinaryNode[Expression] {
@@ -110,10 +111,6 @@ abstract class LeafExpression extends Expression with trees.LeafNode[Expression]
 
 abstract class UnaryExpression extends Expression with trees.UnaryNode[Expression] {
   self: Product =>
-
-  override def foldable: Boolean = child.foldable
-
-  override def nullable: Boolean = child.nullable
 }
 
 // TODO Semantically we probably not need GroupExpression
@@ -137,5 +134,9 @@ trait ExpectsInputTypes {
 
   def expectedChildTypes: Seq[DataType]
 
-  override def validInputTypes: Boolean = children.map(_.dataType) == expectedChildTypes
+  override def checkInputDataTypes: Option[String] = {
+    // We will always do type casting for `ExpectsInputTypes` in `HiveTypeCoercion`,
+    // so type mismatch error won't be reported here, but for underling `Cast`s.
+    None
+  }
 }